Modular Rotational Device For Torsionally Stabilizing An Endoprosthesis

ABSTRACT

An improved modular rotational device includes a first and second threaded coupler for affixation along the stem of an endoprosthetic device, for example, a humeral prosthesis or a femoral prosthesis. The rotational device axis of rotation is coaxial with the stem, and its axis of rotation is located in close proximity to the intramedullary stem of the prosthesis or in close proximity to the distal articulation of the prosthesis. A housing has a proximal and distal end with an axial bore therethrough for receiving an elongated stem of the device. A lobe ring may be utilized to limit the axis of rotation of the device. Additional endoprosthetic devices may be attached to male or female threaded couplers, or to Morse tapers. A plurality of suture attachments facilitates attachment of soft tissue thereto.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/808,111, filed Nov. 9, 2017; which is a continuation of U.S. patentapplication Ser. No. 15/171,131, filed on Jun. 2, 2016, and issued onNov. 26, 2019, as U.S. Pat. No. 10,485,669; which is a continuation ofU.S. patent application Ser. No. 14/680,897, filed Apr. 7, 2015, and nowabandoned.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to orthopedic implant technology and, morespecifically, to endoprosthetic devices for repairing segmental skeletaldefects of the arm and shoulder or leg and hip of a human patient.

Description of Related Art Including Information Disclosed Under 37 CFR1.97 and 1.98

In human patients, disease or extreme trauma can sometimes necessitatethe repair or replacement of a portion or all of the bones and/or jointsthat comprise a patient's arm or leg. For example, a tumor that affectsthe proximal portion of a patient's humerus can require resection of thediseased portion and fixation of a humeral prosthesis that attempts toduplicate the functionality of the original humerus. Such anendoprosthetic device may typically include the humeral head, shaft, andeven the elbow joint, with affixation at the distal end via a shaftfeature that is cemented into a borehole formed within the remainingulna or radial bone of the patient. While such extreme limb-salvagesurgical repairs are made nowadays on a somewhat routine basis, existingprosthetic device technology falls short with regard to duplication ofthe range of movement of the original joints. Consequently, patients aretypically left with limited functionality of the replaced anatomy due tolimited range of motion. Moreover, patients with such repairs, whoattempt arm movements to the limits of these prosthetic devices oftenweaken or damage the affixation site and may even cause dislocation ofthe shoulder joint, resulting in additional trauma to the bone andsurrounding soft tissue.

The instant inventor made tremendous advances in orthopedic implanttechnology with his invention disclosed in PCT Application No.PCT/US2011/056393 entitled “Modular Humeral Prosthesis WithSpherocentric Feature,” filed on Oct. 14, 2011, the disclosure of whichis incorporated by reference herein for all purposes. As the titlestates, this invention discloses a modular humeral prosthesis having anew and unique spherocentric elbow joint that allows full supination andpronation of the patient's hand post-recovery. However, as with this andother current humeral prostheses it was discovered that upon repeatedmedial and lateral rotation of the patient's repaired arm excessivetorsional stresses were imparted on the humeral prosthesis shaft. In thecase of complete shoulder repairs the excessive torsional stressesresulted in full separation and dislocation of the shoulder joint withresultant damage to the joint and surrounding soft tissue. In the caseof partial humerus repair the excessive torsional stresses resulted in“windshield wiper” loosening of the cemented stem from the fixationsite.

Existing humeral and femoral prosthesis are ineffective in addressingthese realized shortcomings because of the fixed nature of their design.Specifically, existing designs that incorporate a rudimentary bearing orother rotational feature to allow the prosthesis head member to rotateto some degree with respect to the shaft member are limited in use andinflexible in location of the rotational feature with respect to therepaired joint. For example, specific humeral or femoral repairs requireprecise positioning of the rotational device aspect to improve stabilityand reliability of the repair. In the instance in which a humerus isundergoing repair to replace a damaged glenoid, it is beneficial tojoint stability to position the rotational device as near the affixationsite of the repair as practicable to reduce the rotational torqueexperienced by the intramedullary stem of the prosthetic. The instantinvention presents such a positionable rotational device to addressthese and other shortcomings as will be understood by one of ordinaryskill following a thorough study of the embodiments described herein.

BRIEF SUMMARY OF THE INVENTION

The present invention in a first embodiment is drawn to a modularrotational device for torsionally stabilizing an endoprosthetic device,the device comprising: a first threaded coupler including an elongatedstem extending therefrom; a housing having a proximal end and a distalend with an axial bore therethrough; a proximal sleeve positioned withinthe housing proximal end axial bore, the proximal sleeve having an axialbore therethrough for receiving the elongated stem, the proximal sleevereducing the rotational friction of the elongated stem with respect tothe housing proximal end; a distal sleeve positioned within the housingdistal end axial bore, the distal sleeve having an axial boretherethrough for receiving the elongated stem; the distal sleevereducing the rotational friction of the elongated stem with respect tothe housing distal end; a distal fastener for positively engaging theelongated stem within a distal end cavity to retain the stem within thehousing distal end; and a second threaded coupler, the first threadedcoupler and the second threaded coupler for attachment of an additionalendoprosthetic device thereto.

Another embodiment of the device comprises a lobe ring affixed to theelongated stem for limiting the degree of the rotation of the elongatedstem within the housing. Another embodiment of the device comprises alobe ring affixed to the elongated stem, the lobe ring including a rampfeature for gradually arresting the relative joint rotation. Anotherembodiment of the device comprises a lobe ring affixed to the elongatedstem and a rotational stop within a distal end cavity for engaging afeature on the lobe ring for limiting the degree of the rotation of theelongated stem within the housing. Another embodiment of the devicecomprises a distal end cavity including threads for attachment of anadditional endoprosthetic device thereto. Another embodiment of thedevice comprises at least one Morse taper for affixation of anadditional endoprosthetic device thereto. Another embodiment of thedevice comprises a porous mesh metal surface treatment for soft tissuegrowth attachment thereto. Another embodiment of the device comprises aplurality of through hole suture attachments for suture attachment ofsoft tissue thereto. Another embodiment of the device comprises at leastone hex feature for engagement of a gripping tool therewith. Anotherembodiment of the device comprises a hex feature separating the housingproximal end from the housing distal end, the hex member for engagementof a gripping tool therewith.

The present invention in another embodiment is also drawn to a modularrotational device for torsionally stabilizing an endoprosthetic device,the device comprising: a first threaded coupler including an elongatedstem extending therefrom; a housing having a proximal end and a distalend with an axial bore therethrough; and the distal end housingincluding a second threaded coupler, the first threaded coupler and thesecond threaded coupler for attachment of an additional endoprostheticdevice thereto, the first threaded coupler adapted to rotate withrespect to the second threaded coupler.

Another embodiment of the device comprises a proximal sleeve positionedwithin the housing proximal end axial bore, the proximal sleeve havingan axial bore therethrough for receiving the elongated stem, theproximal sleeve reducing the rotational friction of the elongated stemwith respect to the housing proximal end. Another embodiment of thedevice comprises a distal sleeve positioned within the housing distalend axial bore, the distal sleeve having an axial bore therethrough forreceiving the elongated stem; the distal sleeve reducing the rotationalfriction of the elongated stem with respect to the housing distal end;and a distal fastener for positively engaging the elongated stem withina distal end cavity to retain the stem within the housing distal end.Another embodiment of the device comprises a lobe ring affixed to theelongated stem for limiting the degree of the rotation of the elongatedstem within the housing. Another embodiment of the device comprises adistal end cavity including threads for attachment of an additionalendoprosthetic device thereto. Another embodiment of the devicecomprises at least one Morse taper for affixation of an additionalendoprosthetic device thereto. Another embodiment of the devicecomprises a porous mesh metal surface treatment for soft tissue growthattachment thereto. Another embodiment of the device comprises aplurality of through hole suture attachments for suture attachment ofsoft tissue thereto. Another embodiment of the device comprises at leastone hex feature for engagement of a gripping tool therewith. Anotherembodiment of the device comprises a hex feature separating the housingproximal end from the housing distal end, the hex member for engagementof a gripping tool therewith.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

The present invention will be more fully understood by reference to thefollowing detailed description of the preferred embodiments of thepresent invention when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an exploded perspective view of a first embodiment of amodular rotational device of the present invention;

FIG. 2 is a close-up perspective view of the lobe ring utilized in therotational device embodiment;

FIG. 3 is an assembled perspective view of the rotational deviceembodiment;

FIG. 4 is an exploded perspective view of an embodiment of a modularhumeral prosthesis lower extremity device incorporating an embodiment ofthe rotational device;

FIG. 5 is an assembled perspective view of the embodiment;

FIG. 6 is an exploded view of a forearm device for completion of ahumeroulnar/humeroradial articulation with the disclosed embodiment;

FIG. 7 is an embodiment of a modular spacer for use with the modularhumeral prosthesis as disclosed herein;

FIG. 8 is an embodiment of the modular spacer with surface treatment forsoft tissue attachment;

FIG. 9 is another embodiment of the modular spacer with surfacetreatment for soft tissue attachment;

FIG. 10 is an embodiment of a complete modular humeral prosthesis withrotational device, and featuring a reverse shoulder upper extremity andhumeroulnar/humeroradial articulation;

FIG. 11 is an embodiment of a partial modular humeral prosthesis withrotational device, and featuring a normal shoulder upper extremity;

FIG. 12 is an embodiment of a partial modular humeral prosthesis withrotational device, and featuring a humeroulnar/humeroradialarticulation; and

FIG. 13 is an embodiment of a partial modular femoral prosthesis withrotational device, and featuring a normal femoral head.

The above figures are provided for the purpose of illustration anddescription only, and are not intended to define the limits of thedisclosed invention. Use of the same reference number in multiplefigures is intended to designate the same or similar parts. Furthermore,if and when the terms “top,” “bottom,” “first,” “second,” “upper,”“lower,” “height,” “width,” “length,” “end,” “side,” “horizontal,”“vertical,” and similar terms are used herein, it should be understoodthat these terms have reference only to the structure shown in thedrawing and are utilized only to facilitate describing the particularembodiment. The extension of the figures with respect to number,position, relationship, and dimensions of the parts to form thepreferred embodiment will be explained or will be within the skill ofthe art after the following teachings of the present invention have beenread and understood.

DETAILED DESCRIPTION OF THE INVENTION

The following invention makes reference to the glenohumeral articulation(shoulder joint), the humeroulnar/humeroradial articulation (elbowjoint), the acetabulofemoral articulation (hip joint), and thetibiofemoral/patellofemoral articulation (knee joint) of a patient. Withregard to a humerus, the proximal articulation refers to theglenohumeral articulation and the respective distal articulation refersto the humeroulnar/humeroradial articulation. With regard to a femur,the proximal articulation refers to the acetabulofemoral articulationand the respective distal articulation refers to thetibiofemoral/patellofemoral articulation.

FIG. 1 presents an exploded perspective view of a first embodiment of amodular rotational device as described herein and as utilized in theaccompanying claims. As depicted, the modular rotational device (100) inthis embodiment includes a machined axial component having a malethreaded coupler feature (102) that is part of an elongated stem feature(104). The stem feature (104) centers the axial component within amating passage of a machined housing component at a proximal end (110).

The housing component proximal end (110) features a through-hole axialbore within which a proximal sleeve (108) is located. The proximalsleeve (108) in this embodiment utilizes ultra-high molecular weightpolyethylene (UHMWPE), but may be made from any other friction-reducingbiocompatible polymer. The proximal sleeve (108), likewise, has athrough-hole axial bore within which the stem feature (104) ispositioned. A lip on the proximal sleeve (108) prevents the assembledaxial component from directly contacting the housing component (110),thereby reducing rotational friction of the components relative to oneanother.

The stem feature (104) further extends into the distal end of thehousing component (112), which includes an additional axial bore sectionwithin which a distal sleeve (114) is located. As with the proximalsleeve (108), the distal sleeve (114) utilizes UHMWPE as afriction-reducing and biocompatible bearing for rotation of the stem(104) relative the housing (110). The distal end of the stem feature(104) is drilled and tapped to accept a threaded fastener (118). Thethreaded fastener in this embodiment is a hex fastener (118), whichallows for easier manufacturability due to the positive engagement ofhex wrench tools, but may be any fastener known in the art. The use of athread locking material ensures positive retention of the fastener (118)when affixed within a patient.

The fastener (118) also retains a lobe ring (116) on the end of the stem(104). The lobe ring (116) fits within a mating groove feature (120)within the distal end of the housing (112), and is designed to provide apositive and gradual stop to rotation of the stem (104) to preventover-rotation. FIG. 2 is a close-up perspective view of the lobe ring(116) in the present embodiment, showing the features that prevent thisover-rotation. As shown, the lobe bottom (206) is essentially circular,with the lobe top (202) extended in the “Y” direction. Within the matinggroove (120) the lobe top (202) positively engages the mating groove(120) at each extreme of rotation, preventing further rotation (or“over-rotation”). Gradual ramps (204) are included to ease thetransition to the lobe top (202), which slow the rotation within thegroove (120), thereby preventing “hammering” impulse of the rotationaldevice during rapid and full rotation of the prosthesis by the patient.Positive locating flats (208) in the bore of the lobe (116) mate withflats (106) on the stem feature (104) to prevent rotation of the lobe(116) with respect to the stem (104). Another embodiment might utilize alobe ring with a simple tab feature and no ramps, but hammering of therotational device might result.

In another embodiment the lobe ring (116) does not utilize a physicalrotation stop. Inside the patient, this embodiment allows the stem (104)to rotate to the fullest extent allowed by the patient's soft tissue.This can be advantageous because it prevents the harsh rotational stop“hammering” impulses that might be perceived by the patient as with theprevious embodiment. The stops may be removed from within the groove(120), or the ramps may be removed from the lobe ring, making the lobering more circular in shape.

The machined axial component, the housing component, and all other metalcomponents of the embodiment are manufactured from biologicallycompatible and stable metals. In the instant embodiment the axial andhousing components are titanium, but may be surgical stainless steel,niobium, gold, platinum, or the like. Moreover, combinations of metalsand/or biocompatible polymers may also be utilized and are within thescope of the claimed invention. Internal components, likewise, aremanufactured from these same metals and/or polymers. For example, thelobe ring component (116) of the present embodiment is manufactured fromUHMWPE to reduce impulse forces that can result from rapid rotation ofthe device to a limit. However, metals may also be utilized to improvethe wear resistance of the device. In another embodiment, the devicecomprises a combination of metal and polymer coating on the outer wearsurface to soften the impulse. Yet another embodiment may utilize apolymer body with a metal layer on the outer wear surface to improve thewear characteristics while providing a reduction in impulse.

FIG. 3 is an assembled perspective view of the embodiment showing themodular rotational device (100) in its assembled form, as it would beutilized to complete a torsionally stabilized humeral or femoralprosthesis. A male threaded coupler (302) and a female threaded coupler(304) feature allow for the attachment of additional endoprostheticdevices. For example, modular spacers, intramedullary stems, and jointcomponents necessary to construct a complete endoprosthetic may beattached. Further, other embodiments of the modular rotational device(100) might feature only male threaded couplers or female threadedcouplers, or might have the two reversed from that of the presentembodiment. Hexagonal features (306) are provided to allow the use of anopen-end wrench when assembling other prosthesis devices to theembodiment.

The modular rotational device in other embodiments may include combinedjoint features. For example, FIG. 4 presents an exploded perspectiveview of an embodiment of a modular distal humeral prosthesis deviceincorporating an embodiment of the rotational device. The machined axialcomponent (402) is visible, along with the stem feature (404) andproximal sleeve (408) as in the previous embodiment. However, in thisembodiment the distal humeral component housing (410) provides thethrough-hole axial bore that accepts the proximal sleeve (408) and stem(404). A distal sleeve (412) is located within a housing groove, as is alobe ring (414). A fastener (418) and washer (416) retain the lobe ringon the stem (404), with flats (406) on the stem positively locating thelobe ring (416) within the housing groove (420). Completing the distalhumeral component (400) are axle sleeves (422) for supporting a jointaxle (424) within the housing distal end. The axle sleeves (422), aswith the proximal and distal sleeves (408 and 412), are UHMWPEconstruction to reduce friction during rotation. FIG. 5 is an assembledperspective view of this embodiment.

To complete the construction of a humeral prosthesis with a humeroulnararticulation, it is helpful to describe the device that, when combinedwith the previous embodiment, may form the humeroulnar articulation.FIG. 6 is an exploded view of a forearm device for completion of ahumeroulnar/humeroradial articulation with the disclosed invention. Asshown, an intramedullary ulnar stem (620) features longitudinal grooves(618) extending from the distal end to the proximal end of the stem forrotational stability when cemented into the patient's ulna or radius.Also featured is a taper segment (616) that is also coated with a meansfor apposition of bone (i.e., texture or chemical treatment). Theproximal end of the ulnar stem (620) includes a shaft segment (614) thatfits within and passes through a first thrust sleeve (610) and a secondbearing sleeve (606), and ultimately engages within the positiveengagement flats (208) of a lobe ring (604) similar to that depicted inFIG. 2. A lobe ring fastener (602) engages the ulnar stem shaft (614)and retains the assembly. The sleeves (610 and 606) fit within machinedrecesses within the elbow assembly (600) body. The first thrust sleeve(610) features a thrust surface that minimizes friction between theulnar stem taper (616) and the elbow assembly body (608). The thrustsurface is comprised of the same plastic as the sleeve (610). However,the thrust surface may also be comprised of a suitable medical grademetal or polymer different from that of the sleeve.

To afford rotation and to minimize friction while doing so, the ulnarstem shaft (614) utilizes similar materials as the articulatingsurfaces. For example, the shaft may be coated with cobalt chrome,pyrocarbon, ceramic, or other medical-grade, corrosion inhibiting,friction-reducing material. Likewise, the plastic sleeves (610 and 606)may utilize a medical-grade polymer, including UHMWPE, to reducefriction.

The lobe ring (604) in this embodiment is similar in form and functionto the previously discussed lobe ring. As shown, a positive engagementfeature is provided that mates (or interlocks) with a related feature(612) on the ulnar stem shaft (614), causing the lobe ring and ulnarstem to rotate in unison. A tab feature (624) on the outer radius of thelobe ring (604) moves within a rotational groove feature (622) in thebody (608) and serves to limit the degree of rotation within the elbowassembly body (608). In this embodiment the groove (622) is machinedwithin the elbow assembly body (608) and is sized to allow the ulnarstem (620) to rotate approximately 180 degrees to approximate the normalrange of rotational motion of a patient's wrist and hand, with the tabfeature (624) contacting the ends of the groove feature (622) as inprevious embodiments. The overall range of motion may be adjusted bychanging the overall length of the rotational groove (622) to eitherincrease or decrease this range (i.e., greater than or less than 180degrees). Further, in another embodiment, the lobe ring is a machinedfeature of the ulnar stem shaft (420).

FIG. 7 is an embodiment of a modular spacer for use with the modularhumeral prosthesis as disclosed herein. The overall length of the spacer(700) allows the surgeon to size the resulting humeral prosthesis to fitthe patient's anatomy. For example, a surgery center might maintainmodular spacers in various lengths—10 mm to 50 mm—that afford theability to tailor the length of the repair in 10 mm increments to fitthe patient.

The proximal end of the spacer features a Morse taper (702) followed bythreads (704) for engaging a mating female end on another spacer. TheMorse taper is a common machined taper that is used to positively joinmachined components. The proximal end (708) of the body of the spacerincludes holes (706) for suture attachment of soft tissue. As with themodular rotational device embodiments, the body includes a hex feature(712) for engagement by an open-ended wrench of appropriate size, whichis used during assembly of the modular devices. The distal end (710)features a complementary female threaded coupler (not visible) forengaging with the male threaded coupler (see 702/704) of another spaceror rotational device.

FIG. 8 is an embodiment of the modular spacer with surface treatment forsoft tissue attachment. The proximal (802) and distal (804) bodysegments provide through-hole suture attachment features (806) and alsoincludes a porous mesh surface treatment (808). FIG. 9 presents yetanother embodiment of the modular spacer with surface treatment for softtissue attachment. In this embodiment the spacer provides only femalethread couplers (902) for attachment. Visible once more are the sutureattachment through holes (904) and surface texture (906), and hex wrenchfeature (908). The porous mesh surface treatment creates athree-dimensional surface structure that is similar to cancellous bone,and which encourages the attachment of soft tissue. The porous meshsurface treatment is created using the known process for creating commontrabecular metal, albeit with a greater porosity. For example, thesurface texture may be created by thermal deposition in which thetexture is effectively “printed” onto the surface atom-by-atom.Biocompatible materials, including tantalum, may be utilized in thisprocess to create the three-dimensional surface texture structure. Inthe instant invention, it has been shown that a surface texture porosityof approximately 600 to 800 microns encourages soft tissue attachment totreated implants. Suturing the soft tissue to the suture attachmentfeatures (906) allows the soft tissue to affix to the surface structure(906) as the patient heals.

A successful limb-sparing procedure for oncological purposes can bedivided into three stages. The first stage involves tumor resection, andmust spare significant tissue structures to support reconstruction whileobtaining adequate oncologic margin to eliminate diseased tissue. Thesecond stage involves the affixation of a stable, painless skeletalreconstruction (typically an endoprosthetic device). Third, thesurrounding and supporting soft tissue is required to restorefunctionality to the skeletal reconstruction. The performance of thefirst two steps of this procedure is well understood, so it is notnecessary to provide such detail herein. However, the endoprostheticdevice and its use disclosed herein have heretofore never beencontemplated.

FIG. 10 presents an embodiment of a complete modular humeral prosthesiswith rotational device, and featuring a reverse shoulder upper extremityand humeroulnar/humeroradial articulation (1000). The metaphysealsegment (1002) in this embodiment provides a spherical insert forengagement with a metal ball fixated within the glenoid cavity of thepatient. The shaft is comprised of any number and size of modularspacers (800, 900) necessary to achieve the correct length for therepair. The lower extremity (400) features a rotational device (1006) aspreviously described, as well as a forearm device (600) to form thehumeroulnar articulation. The intramedullary stem (1004) is affixedwithin an axial borehole in the ulna or radius of the patient. Normallyduring surgery the intramedullary stem (1004) is affixed to thepatient's ulna. Following resection of the appropriate length of theulna, the medullary canal is reamed to receive the stem (1004) to adepth up to the stem taper and is packed with cement. If the prostheticdevice is being fixated in the patient's right arm, the stem (1004) isrotated counterclockwise as viewed from the distal end to the stop ofits rotation and, with the patient's palm facing skyward, the stem isinserted into the medullary canal. The longitudinal channels of theulnar stem in conjunction with the cement provide rotational stabilitywithin the ulna. if the patient's ulna is not serviceable, then thedevice may also be affixed to the patient's radius in the same fashion.

To complete the procedure (third stage) it is necessary to reattach thesurrounding and supporting soft tissue to the prosthesis. The presentembodiment provides a porous mesh surface treatment and strategic sutureattachments to effect reattachment. For example, the subscapularis mustbe reattached to the area of the prosthetic device that represents thelesser tuberosity of the original humerus (1006). The subscapularistendon is affixed to a suture attachment feature in this area (1006)and, over time, the tendon collagen fibers anchor the tendon into theporous mesh surface treatment present at this enthesis. Likewise, thepectoralis major must be reattached to the area of the prosthetic devicethat represents the lateral lip of intertubercular groove of originalhumerus (1008). Accordingly, the pectoralis major tendon is affixed to asuture attachment feature in this area (1008) and, over time, thistendon collagen fibers anchor the tendon into the porous mesh surfacetreatment present at this enthesis. This is repeated for the remainingmuscles, including the rotator cuff muscles, triceps, brachialis, andbrachioradialis (1010).

FIG. 11 is an embodiment of a partial modular humeral prosthesis withrotational device, and featuring a normal shoulder upper extremity. Thisconfiguration may be used in instances in which resection of a diseasedproximal portion of a humor leaves sufficient shaft length for insertionand affixation of an intramedullary stem (1104) through common means.The metaphyseal segment (1102) includes a ball component (1106) forengagement with the glenoid process of the patient, or with a glenoidprosthetic device. A rotational device (100) as described herein is alsoincluded, with the rotational aspect nearest to the stem (1104). It ispossible to add additional modular spacers (1108) to establish theproper length of the repair to ensure symmetry with regard to thepatient's arms.

FIG. 12 is an embodiment of a partial modular humeral prosthesis withrotational device, and featuring a humeroulnar/humeroradialarticulation. This endoprosthetic device configuration (1200) may beused in instances in which the humeroulnar/humeroradial articulationmust be resected due to disease, yet the glenohumeral articulation isretained. As shown, a proximal intramedullary stem (1202) is affixedwithin the patient's remaining humerus shaft segment, and a radialintramedullary stem (1208) is affixed within the patient's remainingradius shaft segment. A modular rotational device (100) is included,with the rotational device (1204) nearest the humeral stem (1202). Amodular spacer (900) is incorporated as necessary to establish theproper repair length to ensure symmetry of the patient's arm length. Themodular spacer (900) includes porous mesh metal surface treatment toensure affixation of the soft muscle tissue of the forearm.

The rotational device embodiment may also be utilized with femoralprosthetic devices to, likewise, prevent excessive torsional stressesduring rapid full rotation of the patient's lower leg with respect tothe hip. These torsional stresses can weaken the stem fixation site, andcan cause dislocation of the acetabulofemoral articulation (hip socket)due to the impulse felt at the acetabulofemoral articulation at fullrotation. As with the humeral prosthetic device, the rotational deviceis positioned proximate the intramedullary stem. Such a configuration isdepicted in FIG. 13.

FIG. 13 is an embodiment of a partial modular femoral prosthesis withrotational device, and featuring a normal femoral head. Thisendoprosthetic device configuration (1300) utilizes the modularrotational device (100) as described herein, coupled with the trochantersegment (1302) featuring a ball component (1308) for engagement with theacetabulum. The modular rotational device (100) is positively retainedby the trochanter segment (1302) through use of a hex- headed lockingscrew (1304) that runs the length of the trochanter segment (1302). Asdepicted, the outer surface of the proximal segment (1302) includes aporous mesh surface treatment as previously described, to effect softtissue attachment to the prosthesis. Suture attachment features (1306)provide for positive retention of the soft tissue until healing andattachment occurs.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive. Accordingly, the scope of theinvention is established by the appended claims rather than by theforegoing description. All changes that come within the meaning andrange of equivalency of the claims are intended therein. Further, therecitation of method steps does not denote a particular sequence forexecution of the steps. Such method steps may therefore be performed ina sequence other than that recited unless the particular claim expresslystates otherwise.

I claim:
 1. A modular rotational device for torsionally stabilizing anendoprosthesis bone segment located wholly internal to a patient, thedevice comprising: a first threaded coupler (302) including an elongatedstem (104) extending therefrom; a housing having a proximal end (110)and a distal end (112) with an axial bore therethrough; a proximalsleeve (108) positioned within the housing proximal end axial bore, theproximal sleeve having an axial bore therethrough for receiving theelongated stem, the proximal sleeve reducing the rotational friction ofthe elongated stem with respect to the housing proximal end; a distalsleeve (114) positioned within the housing distal end axial bore, thedistal sleeve having an axial bore therethrough for receiving theelongated stem; the distal sleeve reducing the rotational friction ofthe elongated stem with respect to the housing distal end; a distalfastener (118) for positively engaging the elongated stem within adistal end cavity to retain the stem within the housing distal end; anda second threaded coupler (304) on the distal housing end, the firstthreaded coupler and the second threaded coupler each adapted to acceptan additional complementary threaded endoprosthesis device, the firstthreaded coupler rotatable with respect to the second threaded couplerpost-fixation within a patient.
 2. The device of claim 1, the devicefurther comprising: a metaphyseal segment (1002) coupled to the firstthreaded coupler (302) or second threaded coupler (304).
 3. The deviceof claim 1, the device further comprising: a forearm device (600)coupled to the first threaded coupler (302) or second threaded coupler(304).
 4. The device of claim 1, the device further comprising: at leastone modular spacer (800, 900) coupled to the first threaded coupler(302) or second threaded coupler (304), wherein the number of modularspacers is chosen to establish the overall length of the device toapproximate the length of a resected patient bone segment.
 5. The deviceof claim 1, the device further comprising: an intramedullary stem (1104,1202) coupled to the first threaded coupler (302) or second threadedcoupler (304).
 6. The device of claim 1, the device further comprising:a trochanter segment (1302) coupled to the first threaded coupler (302)or second threaded coupler (304).
 7. A modular rotational device fortorsionally stabilizing an endoprosthesis bone segment located whollyinternal to a patient, the device comprising: a first threaded coupler(302) including an elongated stem (104) extending therefrom; a housinghaving a proximal end (110) and a distal end (112) with an axial boretherethrough; and the housing distal end including a second threadedcoupler (304), both the first threaded coupler and the second threadedcoupler each adapted to accept an additional complementary threadedendoprosthesis device, the first threaded coupler rotatable with respectto the second threaded coupler post-fixation within a patient.
 8. Thedevice of claim 7, the device further comprising: a metaphyseal segment(1002) coupled to the first threaded coupler (302) or second threadedcoupler (304).
 9. The device of claim 7, the device further comprising:a forearm device (600) coupled to the first threaded coupler (302) orsecond threaded coupler (304).
 10. The device of claim 7, the devicefurther comprising: at least one modular spacer (800, 900) coupled tothe first threaded coupler (302) or second threaded coupler (304),wherein the number of modular spacers is chosen to establish the overalllength of the device to approximate the length of a resected patientbone segment.
 11. The device of claim 7, the device further comprising:an intramedullary stem (1104, 1202) coupled to the first threadedcoupler (302) or second threaded coupler (304).
 12. The device of claim7, the device further comprising: a trochanter segment (1302) coupled tothe first threaded coupler (302) or second threaded coupler (304).